Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portionthereof with transitional graphical user interface showing my newdesign; and,

FIG. 2 is the second image thereof.

The dash-dash broken lines around the figure show a display screen orportion thereof that forms no part of the claimed design; the dash-dashbroken line with in the figures show unclaimed portions of the graphicaluser interface. The dot-dash broken lines within the figures representan unclaimed boundary line that forms no part of the claimed design.

The appearance of the transitional image sequentially transitionsbetween the images shown in FIGS. 1-2. The process or period in whichone image transitions to another image forms no part of the claimeddesign.

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 